Process of producing sheets from corrosion-resistant ferrous-base alloys combining improved strengh properties with corrosion resistance



Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE SIOhl RESISTANCE Victor B. Lawrence, Norristown, Pa., assignor to Alan Wood Steel Company, a corporation oi Pennsylvania No Drawing. Application May 25, 1935,

' Serial No. 23,520

6 Claims. 01. 1411-12) This invention relates to the production of rolled iron and steel sheets and plates characterized by relatively high resistance to rust and corrosion, and having high tensile strength and ductility as well as other physical properties that make for ease oi fabrication by methods involv- L ing welding, bending and similar operations.

It has long been common'practice to cold roll iron and steel to obtain increased strength. However, cold rolling has the disadvantage that, it lowers the corrosion resistance of the metal. Therefore, cold rolling is not applied where itis desired that the finished sheet or plate shall have a high resistance to corrosion, and, consequently,

15 it has not been practical to produce cold rolled sheets and plates from special iron and steel alloys designed by reason 01 their composition to have high corrosion resistance. In other twordsfthe sacrifice of corrosion resistance of these alloys has been such as to make it unatftractive trom the commercial standpoint to cold roll them to obtain highstrength. Zlherefore, where it is desired to produce sheets and plates having both high corrosion resistance and high strength, resort has been had to special iron and steel alloys combining to a greater or lesser extent the properties of high strength and corrosion resistance when the alloy is formed into sheets or plates by hot rolling.

Steel sheets of high strength have been prbduced by the alloying of ironwith hardening elements-carbon, manganese, chromium, nickel, molybdenum, etc., but the fabrication by welding of such iron alloys has involved difiiculties which have made them commercially undesirable, and the maximumweldable limits of ferrous alloys hardened by additions cf one of the above elements, or combinations of these elements established by the present welding technique, are too low to permit more than moderate increases in strength.

Summarizing the abovefsheets and light structural shapes formed from iron or steel alloy combining higher resistance to corrosion, high strength, and good welding properties, have not been available'at a reasonable cost of production.

I have found that by appropriate selection of the iron or steel an with respect to workability and resistance to corrosion, and conducting the rolling operation in the manner hereinafter more particularly described, it is possible to produce sheets, plates and other relatively thin'structural shapes having the high 55 strength and other desirable physical properties that are obtainable by cold rolling and at the same time either beneficially afifect, or at least not materially decrease, the corrosion resistance properties of the alloy. as compared with those that would be exhibited by a similar alloy worked by the hot rolling process.

According to my invention a copper-containing iron or steel alloy, of the ferritic type and of a suitable composition to exhibit resistance to corrosion and at the same time readily rollable when heated, and in the iorm of a slab or billet of suitable thickness, is heated to a temperature above or within the upper critical range and then rolled while accelerating the cooling of the metal by applying water or any other cooling medium,

this being continued until the metal has cooled or quenched to below the critical range. The rolling may be continued after the temperature is below the critical range, in this way combining the eflect of cold rolling and quenching and imadvantageously carried out in a conventional three-high rolling mill through which the pieces are passed to and fro. A tilting table is provided at each side of the mill to catch the pieces as they are rolled and lii't'them into the return pass. The starting materlal,billet, slab, plate or break-downis broughtat the appropriate temperature from a furnace disposed conveniently near theentering side of the mill. The rolls" are kept cool by means of water sprays which prevent change in shape of the rolls due to heating and at the same time promoting the cooling of the pieces being passed, through the rolls. The process can also be carried out on mills other than the conventional three-high rolling mill, for example, two-high or four high continuous mills, providing the material is cooled and quenched during the rolling operation by the application of water or other cooling medium.

The process is applicable to a wide range of copper-containing iron and steel alloys of the non-austenitic or ferritic type. One advantage of the present invention resides in the fact that relatively cheap iron and steel alloys may be so improved with respect to their strength and other physical properties as to meet strength and corrosion resistance specifications that heretofore could only be met by resort to more expensive iron and steel alloys. A group of relatively inexpensive corrosion resistant iron and steel alloys that are amenable to the process and can be formed into sheets and plates having relatively high strength without detrimental effect on their corrosion resistance, are those coppercontaining iron and steel alloys in which the carbon content is kept under 0.50%, the copper is under 0.80%, and phosphorus is less than 0.10%. I have found, for example, that improvement in strength values of the order noted below maybe obtained by rolling a copper-bearing steel of the following analysis range under the conditions of accelerated cooling hereinbefore described: 8

Percent .C--- 0.1 0.3 Mn 0.30-0.70 S- Under 0.04 P- .os-o.1o C11 0.35- .50

Elastic limit ultimaltf lbs/sq. in. 'g

Ordinary liotrolled 33,000 saoocssom Present process 70,000 90,000

and, what is particularly important, these values are obtainable without adversely affecting the corrosion resistance of the alloy.

Although the invention makes possible the sub- 0 stitution of relatively inexpensive copper-containing iron and steel alloys for more expensive alloys that have heretofore been considered essential to obtain desired combinations of corrosion resistance and strength, it will be under stood thatthis does not mean necessarily thatv the more expensive ferrous-base copper-containing alloys will be rendered uninteresting from the commercial standpoint by reason of the improvement in the properties 01' cheaper alloys that is made possible by my process. On the contrary, my process makes it possible to so improve the properties of. some of the more ex-' pensive alloys as to widen their field of useful-.

ness. Commercially available copper-containing alloy steels oi the territic type which oiler this prospect are those containing in appropriate amounts or combinations, chromium, copper, manganese, molybdenum, nickel, silicon, phosphorus or vanadium. i

In carrying out the rolling operation the temperature at which the slab or other partially reduced shape is brought to the rolls will vary somewhat depending on the'thickness of the slab and the thickness desired in the finished sheet or plate. The thickness of the slab brought to the rollingoperation should also beconsidered in relation to the temperature, the extent of the reduction required and the time involved in efiecting the reduction, so asto insure that a suitable relation is maintained between the rate oi cool ing of the material as it undergoes rolling and quenching and the rate ofreduction to the desired thickness. In the case of heavier sheets,

say, %"-fi;" in thickness, the slab, should be steel in the Ac1-Ac3 range.

quenching should then be continued, the larger would tend to nullify the results of the accelerated cooling and rolling treatment. At the same time, further improvement in the strength properties of the sheet is brought about in this final stage under conditions approaching those of cold rolling but without the detrimental effects on the "corrosion resistance of the product that is characteristic of cold rolling.

When starting with pieces that have already been'brought down to a relatively thin crosssection by hot rolling, they may be brought to the combined quenching and rolling operation of the present invention at a temperature within the A03 critical range. For example, starting with steel sheets or break-downs that have been hot rolled to and which it is desired to re-.

duce to sheets of 1%" thickness, the temperature at t e beginning-'of-the combined quenching and rolling operation may be about 1600 F.

While the invention has been described with particular reference to the production of sheets, it will be understood that beneficial results may cross-section such as light plates and strips. In fact, any structural shape that may be formed be obtained in producing other products of thin I by rolling and having a cross-section of a simstricted sense in the rolling industry but also. billets, plates and sheets which have been pre-'- liminarily worked by hot rolling from the original cast ingots, and which are intended to be further reduced to bring them to final dimension.

I claim:

1. The process of working and heat treating corrosion resista'nt copper-containing ferrousbase alloys of the ferritic type to produce structural shapes of thin cross-section having improved physical properties, which comprises heating a'copper-containing ferrous-base alloy of corrosion resistance analysis and of thefer ritic type' to a temperature at least approximating the upper critical point, and then hot rolling with accelerated cooling of the metal during the rolling operation, and continuing said combined rolling and accelerated cooling 'until the temperature of the metal throughout its section has been brought below the lower critical range.

2. Theprocess of producing structural shapes of thin cross-section with improved strength properties from corrosion resistant copper-containing ferrous-base alloys of the ferritic type without substantially impairing the corrosion resistance of the alloy, whichcomprises subjecting a copper-containing ferrous-base alloy or corrosion resistance analysis and of the ferritic type to hot rolling while accelerating the cooling of the metal by applying a liquid quenching medium thereto, continuing said combined rolling and quenching treatment until the temperature of the metal throughout its section has been brought below the lower critical range, and continuing the rolling treatment to eflect further reduction of the thickness and to improve the strength properties of the rolled shape.

3. Process of producing sheets with improved strength properties from corrosion resistant copper-containing ferrous-base alloys of the ierritic type without detrlmentally aiiecting the corrosion resistance of the alloy, which comprises sub- Jecting a copper-containing ferrous-base alloy of corrosion resistance analysis, containing not more than 0.5% carbon and of the ierritic type,

to hot rolling to produce a slab of desired thickness for the succeeding working and heat treatment, heating the slab to a temperature at least approximating the'upper critical point, then sub- Jecting the thus heated slab to rolling while an accelerating the cooling hi the metal by applying a quenching medium thereto during the rolling operation, and continuing said combined rolling and quenching treatment until the temperature oi the metal throughout its section has been brought below the lower critical range.

4, Process of producing sheets with improved structural properties from corrosion resistant copper-containing ferrous-base alloys 01' the i'erritic type without detrimentally aii'ecting the corrosion resistance of the alloy, which comprises subjecting a copper-containing ferrous-base alloy oi corrosion resistance analysis, containing not more than'0.5% carbon and of the ferritic type to hot rolling to produce a slab oi desired thick- 35 ness tor the succeeding working and heat treatment operations, heating the slab to a tempera- VICTOR H. LAWRENCE.

ture at least approximating the upper critical point, then simultaneously subjecting the heated 'the alloy, which comprises subjecting a coppercontaining ferrous-base alloy of corrosion resistance analysis, containing not more than 0.5% carbon and oi the ierritic type to hot rolling in a three-high rolling mill while accelerating the coolingoi the metal by applying sprays of water thereto during the rolling operation, and continuing said combined rolling and quenching treatment until the temperature of 'the metal has been brought below the lower critical range.

6. Process of producing sheets with improved structural properties from copper-containing ferrous-base alloys without detrimentally aflect-,

ing the corrosion resistance of the alloy, which comprises heating a hot rolled slab of a coppercontaining ferrous-base alloy of the ierritic type to a temperature at least approximating the upper critical point, then simultaneously subjecting said slab to rolling and quenching and continuing said combined rolling and quenching treatment until the temperature of the rolled product has been brought below the lower critical range;

VICTOR H. LAWRENCE.

CERTIFICATE OF G ORREGTI ON February 15, 958.

It. hereby certified that error appears in the printed specification of the above number ed patent requiring correction as follows: Page 2, second column, line 71, claim 2, for the word "or" read of; and that the said Letters Patent should-be read with this correction therein that the same nay conform to the record of the case in the Patent Office.- i

= Signed and sealed this 29th day of March, A. r n.

Henry van' tr'sdale,

Acting Commissioner of Patents.

quenching treatment until the temperature of the metal throughout its section has been brought below the lower critical range, and continuing the rolling treatment to eflect further reduction of the thickness and to improve the strength properties of the rolled shape.

3. Process of producing sheets with improved strength properties from corrosion resistant copper-containing ferrous-base alloys of the ierritic type without detrlmentally aiiecting the corrosion resistance of the alloy, which comprises sub- Jecting a copper-containing ferrous-base alloy of corrosion resistance analysis, containing not more than 0.5% carbon and of the ierritic type,

to hot rolling to produce a slab of desired thickness for the succeeding working and heat treatment, heating the slab to a temperature at least approximating the'upper critical point, then sub- Jecting the thus heated slab to rolling while an accelerating the cooling hi the metal by applying a quenching medium thereto during the rolling operation, and continuing said combined rolling and quenching treatment until the temperature oi the metal throughout its section has been brought below the lower critical range.

4, Process of producing sheets with improved structural properties from corrosion resistant copper-containing ferrous-base alloys 01' the i'erritic type without detrimentally aii'ecting the corrosion resistance of the alloy, which comprises subjecting a copper-containing ferrous-base alloy oi corrosion resistance analysis, containing not more than'0.5% carbon and of the ferritic type to hot rolling to produce a slab oi desired thick- 35 ness tor the succeeding working and heat treatment operations, heating the slab to a tempera- VICTOR H. LAWRENCE.

ture at least approximating the upper critical point, then simultaneously subjecting the heated 'the alloy, which comprises subjecting a coppercontaining ferrous-base alloy of corrosion resistance analysis, containing not more than 0.5% carbon and oi the ierritic type to hot rolling in a three-high rolling mill while accelerating the coolingoi the metal by applying sprays of water thereto during the rolling operation, and continuing said combined rolling and quenching treatment until the temperature of 'the metal has been brought below the lower critical range.

6. Process of producing sheets with improved structural properties from copper-containing ferrous-base alloys without detrimentally aflect-,

ing the corrosion resistance of the alloy, which comprises heating a hot rolled slab of a coppercontaining ferrous-base alloy of the ierritic type to a temperature at least approximating the upper critical point, then simultaneously subjecting said slab to rolling and quenching and continuing said combined rolling and quenching treatment until the temperature of the rolled product has been brought below the lower critical range;

VICTOR H. LAWRENCE.

CERTIFICATE OF G ORREGTI ON February 15, 958.

It. hereby certified that error appears in the printed specification of the above number ed patent requiring correction as follows: Page 2, second column, line 71, claim 2, for the word "or" read of; and that the said Letters Patent should-be read with this correction therein that the same nay conform to the record of the case in the Patent Office.- i

= Signed and sealed this 29th day of March, A. r n.

Henry van' tr'sdale,

Acting Commissioner of Patents. 

